Dryocosmus kuriphilus has become a major threat to Castanea sativa and chestnut cultivation in Europe since its discovery in Italy in 2002. Thankfully, the biological control agent Torymus sinensis has proven to effectively control and reduce the D. kuriphilus population. The reaction of chestnut trees to decreasing D. kuriphilus pressure, however, has been sparsely investigated. In this study, we analyze the recovery patterns of chestnut trees since the pest epidemic peak in 15 sites in southern Switzerland that were differently affected by the dephased arrival of D. kuriphilus and T. sinensis. By using various tree damage and insect population indicators, we show how damage varies as a function of the time elapsed between pest arrival and biological control by T. sinensis. Specifically, trees in sites experiencing seven years of D. kuriphilus uncontrolled attacks show large dying crown portions and stress-induced reactions (e.g., suckers along the stem) compared to sites where the two insects arrived nearly simultaneously. Moreover, in warm and south-exposed sites, the D. kuriphilus population remains significant and damage on chestnut trees still persists suggesting a desynchronisation in the phenology of the antagonist with respect to the pest.